Ventilation questions

[ßudzilla]

I'm not so sure I'm really understanding the ventilation/CFM calculation. I'm using a 2x2x4 tent and according to the LxWxH calc. I would only need a fan rated for 16 CFM, which just seems absurdly low. I have this tent set up in my basement which is unfinished and more or less an open layout. On an average day it gets to about 25c and 30c on our hotest, and I keep it around 20-21c inside.

I have a MH/HPS cool tube setup that can go up to 600w and dim to 250w, what would be my best option here? If I can control the heat, crank it all the way up to 600? Another issue I have is the vent holes on the tent are only 4in, while the cooltube is 6in. Should get a 4in inline fan/duct or 6in and just use flange adapters, and how many CFM should I be looking for with this setup?

Edit; sorry, 2x2x4=16/3, so really i'd only need about 5 CFM, according to that. That makes no sense to me?

Ah my bad. I'm not taking into account the heat/btu output. I'm struggling to find a decent calculation for that though.

 

[TheFertilizer]

2x2x4 is 16 cubic feet. So virtually every fan on the market is going to be 125-440 cubic feet per minute. You could actually get away with using a small PC computer fan. Anything over 50 cfm will give you adequate air flow.

By 4 inches do you mean 4 inches wide? Even if it 4x4 that is 16 square inches and will give you plenty of air flow. Keep in mind that most fans 4 inches across will be 4xPi^2 in terms of surface area. So in other words even hole if 4x3 inches wouldn't be that limiting.

With a 600 watt bulb you're going to be pulling a fair amount of heat off but I don't know the BTU calculation either. I so know most commercial fans will be adequate airflow to keep your tent ambient temperature. Meaning the same temperature of you intake air will be the temperature in the rent. I wouldn't worry too much about cooling the bulb itself, you're actually robbing lumens from it the cooler it gets, but more importantly you're concern is the tent temperature not the bulb temperature.

If you wanted to run an intake fan the key is to make sure it is equal to or less than the same CFM rating as your exhaust fan. This creates negative pressure in your tent which is good because it will always be sucking in new air line a vacuum and if you have a carbon scrubber it won't leak unfiltered air. Plus having an intake fan makes it easier to filter incoming air to prevent dust, lint, pests and hair from entering the tent. You can use cut-to-fit filters and tape them ove the inlet vents, but intake fans will allow you to use filters that are HEPA certified.

Hope I answered your question. To make a long story short, you could for sure get away with any 400 cfm inline blower fan and maybe even a lesser booster fan. If you wanted an active intake to filter the incoming air, keep your head exhaust CFM greater than other intake. If you don't want filtered intake, using your vents for passive intake should be adequate.

 

[Serpent]

And a good thing about bigger CFM fan on high RH days when the humidity spicks a good inline fan will help control that

 

[ßudzilla]

Alright thanks guys. Another question; Should I have the fan set up outside the tent, and have the cool tube on a "closed circuit" rather than inside the tent? Not sure hot to explain it so instead I threw together this amazing paint picture.

Should I have it set up like this one here:

Or like this one here?

You can also see what I meant by the cooltube is 6in, while the duct and opening to the tent is only 4.

And would this fan be okay? It is only a 4in, 190CFM. Reason I went with 4in is because I don't want to mess around with a bunch of adapters and flanges for the ducting.

 

[ßudzilla]

I don't plan on using a carbon filter if that matters.

 

[Torst]

I am by no means an expert but there is almost no way you will keep that tent cooled properly.

I run a 3x3x7ft tall tent with a 600w MH/HPS with a cool tube with a 6" exhaust and a 460cfm inline fan in a fully finished basement with central air. My temps are still higher than I would like in flower.

Good luck!!!

 

[ßudzilla]

I am by no means an expert but there is almost no way you will keep that tent cooled properly.

I run a 3x3x7ft tall tent with a 600w MH/HPS with a cool tube with a 6" exhaust and a 460cfm inline fan in a fully finished basement with central air. My temps are still higher than I would like in flower.

Good luck!!!

I've seen plenty of others with the same setup with great results. Like I mentioned though I can dim it down to either 400 or 250 if need be.

 

[ßudzilla]

bump

 

[415friendly]

I have a 265 CFM fan in a 2 x 3 x 5 cabinet and had some serious hear problems, even with CFL and/or LED.

You would think that the fan would be able to handle all the heat, but I think the problem is that the volume of air in the small cabinet is so low that it takes almost no time to heat up. More space/bigger tent would mean more buffering capability of the air to absorb the heat energy.

I think you will find that you need to run your HID at very low power to make it manageable.